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Premultiply background color by alpha for images

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* src/xterm.c (x_query_frame_background_color): Premultiply
colors as X wants them when built without Cairo.
This commit is contained in:
Po Lu 2022-02-14 18:39:56 +08:00
parent 4c2701fad1
commit 9844b152a5
1 changed files with 22 additions and 0 deletions
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22
src/xterm.c
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@ -3146,13 +3146,35 @@ static void
x_query_frame_background_color (struct frame *f, XColor *bgcolor)
{
unsigned long background = FRAME_BACKGROUND_PIXEL (f);
#ifndef USE_CAIRO
XColor bg;
#endif
if (FRAME_DISPLAY_INFO (f)->alpha_bits)
{
#ifdef USE_CAIRO
background = (background & ~FRAME_DISPLAY_INFO (f)->alpha_mask);
background |= (((unsigned long) (f->alpha_background * 0xffff)
>> (16 - FRAME_DISPLAY_INFO (f)->alpha_bits))
<< FRAME_DISPLAY_INFO (f)->alpha_offset);
#else
if (FRAME_DISPLAY_INFO (f)->alpha_bits
&& f->alpha_background < 1.0)
{
bg.pixel = background;
x_query_colors (f, &bg, 1);
bg.red *= f->alpha_background;
bg.green *= f->alpha_background;
bg.blue *= f->alpha_background;
background = x_make_truecolor_pixel (FRAME_DISPLAY_INFO (f),
bg.red, bg.green, bg.blue);
background &= ~FRAME_DISPLAY_INFO (f)->alpha_mask;
background |= (((unsigned long) (f->alpha_background * 0xffff)
>> (16 - FRAME_DISPLAY_INFO (f)->alpha_bits))
<< FRAME_DISPLAY_INFO (f)->alpha_offset);
}
#endif
}
bgcolor->pixel = background;